The Hex Factor

Xanthe stared down at the test paper and gasped. A thick line had been slashed across it, and at the bottom, in her own handwriting, were the words, 'Miss Pimm’s maths class stinks'.
Xanthe can’t wait to turn thirteen, but as her birthday nears, her world starts to fall apart. Set up at school, it seems her age-old enemy, Kelly, is making trouble for her.
With her friends deserting her, and mysterious glowing Xs appearing in front of her eyes, Xanthe turns to her great-grandmother for help. But what the old lady tells her will change Xanthe’s life forever…